AAWSAP DIRD, Laser Lightcraft Nanosatellites, November 2010

This Defense Intelligence Reference Document (DIA-08-1011-001), dated 1 November 2010, was prepared by the Defense Intelligence Agency's Defense Warning Office under the Advanced Aerospace Weapon System Applications program. It covers nanosatellite technologies, laser Lightcraft propulsion, a weapon mission selection study and a multi-megawatt laser study. The author recommends that the Department of Defense, working with NASA, bring laser Lightcraft propulsion research back to the United States and restart the Air Force X-50LR test flight program.

From the source:Release of 2026-09-18 Incident: 11/1/10, Las Vegas, Nevada. Released with redactions. This document is a Defense Intelligence Reference Document (DIRD), a technical reference format used by the Defense Intelligence Agency (DIA) to capture baseline knowledge on a specific topic for later analytic use. DIRDs are best understood as reference and synthesis products rather than as original research. It is one of 38 DIRDs produced under the Advanced Aerospace Weapon System Applications Program (AAWSAP) between 2009 and 2011. Because AAWSAP’s scope permitted a broad range of supporting topics, not every DIRD in the series directly concerns aerospace systems or future threat assessment. The following summary reflects the DIRD’s scope and framing at the time of writing and should not be read as implying current validation of the concepts discussed. This DIRD examines laser-propelled “Lightcraft” as a possible low-cost method to launch very small satellites into low Earth orbit by using a remote high-energy laser to supply most of the propulsion energy rather than relying entirely on onboard energy sources. The report combines a survey of nanosatellite trends with a review of “Lightcraft” propulsion concepts, vehicle design, beam-control requirements, and mission studies, and argues that the most promising application is the launch of nano- or pico-satellites, especially Earth- and space-observing payloads of a few kilograms or less. It presents the concept as potentially much cheaper than conventional multistage rockets for very small payloads, while also noting significant practical constraints including strict beam-riding geometry, atmospheric losses, demanding pointing and adaptive-optics requirements, and heavy dependence on large ground-, sea-, or air-based laser infrastructure. Overall, the document presents laser “Lightcraft” as a technically plausible launch concept whose attractiveness depends on whether the supporting laser and beam-control system can be made reliable and economical at operational scale.

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• Average power limited by low thermal conductivity of host material.
• Wavelengths propagate extremely well in clear weather:
- Very low absorption.
- Higher scattering.
The requirements for high average power bulk solid-state lasers are [30]:
• Efficient optical pumping of gain medium:
- Flash lamp or laser diode well matched to absorption band.
- Small wavelength difference between pump and lasing ➔ low quantum defect.
• Efficient heat removal from gain medium:
- Improved heat removal techniques from host.
- Large surface area per unit volume.
- Or, large volume to store heat with low duty cycle operation.
• Gain medium must retain good (correctable) optical quality.
The typical properties of widely used Nd :YAG lasers are [30]:
• 4 nm absorption line width.
• 24% heating from quantum loss.
• Saturation intensity~ 3 kW/cm 2 (at~ 2% dopant).
• Multi- kilowatt average power demonstrated.
• Maximum average power potential ~several hundred kilowatts:
- Heat removal makes continuous running a challenge at this power.
- Current high-energy SSLs produce great amounts of heat (e.g., 600 kW of
electrical power in and 100 kW of beam power out equals 500 kW of waste
heat).
- Must store the waste heat and reject it from the system at a lower rate, thus
requiring storage and limited duty cycle.
• Quantum defect = pump light photon energy minus laser light photon energy.
The typical properties of widely used Yb:YAG lasers are [30]:
• 18 nm absorption line width.
• Indium gallium arsenide (InGaAs) pump laser diodes at 0.941 μm wavelength:
- 8.6% heating from quantum loss.
• Saturation intensity ~ 9. 7 kW/cm 2 (at ~ 25% dopant).
• Multi-kilowatt average power demonstrated.
• Maximum average power potential is perhaps 5 x Nd:YAG laser.
A new technology that enables the scaling-up of BSSSL beam power is a recently
developed thermal management system that is used to remove and store the waste
heat produced by BSSSL devices. General Atomics' Advanced Power Systems Division
recently announced * that it has completed testing of an advanced thermal energy
' Reported in Space War Newsletter, June 7, 2010 .
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